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Method for quantitative detection of nugget crack by using energy equivalent of acoustic emission signal in resistance spot-welding process

An acoustic emission signal and resistance spot welding technology, which is applied in the field of quantitative detection of nugget cracks using acoustic emission signal energy equivalent in the resistance spot welding process, can solve the problem that the nugget nucleation process cannot be directly observed and judge the quality of resistance spot welding joints problems such as difficulties and great hazards to the quality of solder joints, achieving the effect of low design and manufacturing costs, simple evaluation methods, and strong practicability

Active Publication Date: 2014-03-26
CHONGQING UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
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Problems solved by technology

However, in the process of resistance spot welding, the nucleation process of nugget cannot be directly observed, which makes it difficult to judge the quality of resistance spot welding joints
In particular, defects such as cracks hidden inside the resistance spot welding nugget are common welding defects in resistance spot welding quality inspection, which not only have great harm to the quality of solder joints, but are also not easy to be detected

Method used

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  • Method for quantitative detection of nugget crack by using energy equivalent of acoustic emission signal in resistance spot-welding process
  • Method for quantitative detection of nugget crack by using energy equivalent of acoustic emission signal in resistance spot-welding process
  • Method for quantitative detection of nugget crack by using energy equivalent of acoustic emission signal in resistance spot-welding process

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Experimental program
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Effect test

Embodiment 1

[0036] The workpiece to be welded is the lap joint of two aluminum alloy sheets with a thickness of 2 mm. The main welding process parameters used are: the welding current is 22000A, the welding current duration is 8 cycles, and the electrode pressure is 0.15MPa.

[0037] During welding, the structural load acoustic emission signal of the resistance spot welding process is collected in real time, and the dynamic curve of the structural load acoustic emission signal is drawn by the analysis software, such as figure 1 shown.

[0038] Different stages of the welding process can be identified from the waveform diagram, and the crack signal 1 can be extracted, such as figure 2 shown.

[0039] Statistical analysis of the amplitude distribution of crack acoustic emission signal pulses. According to this distribution, the magnitude of the magnitude is divided into 10 levels, namely M 1=0.3, M 2 =0.6, M 3 =0.9, M 4 =1.2, M 5 =1.5, M 6 =1.8, M 7 =2.1, M 8 =2.4, M 9 =2.7, M ...

Embodiment 2

[0044] The workpiece to be welded is the lap joint of two aluminum alloy sheets with a thickness of 2 mm. The main welding process parameters used are: the welding current is 22000A, the welding current duration is 8 cycles, and the electrode pressure is 0.15MPa.

[0045] During welding, the structural load acoustic emission signal of the resistance spot welding process is collected in real time, and the dynamic curve of the structural load acoustic emission signal is drawn by the analysis software, such as Figure 5 shown.

[0046] Different stages of the welding process can be identified from the waveform diagram, and the crack signal 1 can be extracted, such as Image 6 shown.

[0047] Statistical analysis of the amplitude distribution of crack acoustic emission signal pulses. According to this distribution, the magnitude of the magnitude is divided into 10 levels, namely M 1 =0.3, M 2 =0.6, M 3 =0.9, M 4 =1.2, M 5 =1.5, M 6 =1.8, M 7 =2.1, M 8 =2.4, M 9 =2.7, M...

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Abstract

The invention provides a method for quantitative detection of nugget crack by using energy equivalent of an acoustic emission signal in a resistance spot-welding process. The method comprises the following steps: acquiring a structural load acoustic emission signal of the resistance spot-welding process in real time, drawing a dynamic oscillograph; extracting the acoustic emission signal of the crack; counting amplitude distribution; dividing the amplitude into a plurality of grades Mi, and accumulating according to ringing count Ni of the acoustic emission signals exceeding each amplitude grade, respectively, to obtain the log value log10Ni of the ringing count, so as to obtain a splattering distribution diagram; fitting a straight line to form a right triangle, calculating out the area, so as to obtain the energy equivalent of the corresponding resistance spot-welding nugget crack; setting an energy equivalent threshold value, determining an acoustic emission source to be a low-energy acoustic emission source when the energy equivalent is lower than the threshold value, and determining the acoustic emission source to a dangerous crack acoustic emission source when the energy equivalent is higher than the threshold value. Due to the adoption of the method, the grade and size of the resistance spot-welding nugget crack defect can be evaluated relatively exactly and quantitatively, and the rapid and nondestructive detection for the nugget crack is realized.

Description

technical field [0001] The invention relates to a nondestructive testing method for quantitatively detecting nugget cracks by using the energy equivalent of acoustic emission signals obtained by real-time detection in the resistance spot welding process, and is suitable for rapid detection of the nugget quality of resistance spot welding of commonly used metal sheet structural materials. Background technique [0002] Resistance spot welding is a welding method widely used in automobile manufacturing, and there are about 3000-6000 resistance spot welding spots on a modern car. Therefore, the quality detection of resistance spot welding solder joints is very important. High-efficiency solder joint quality sensing and its detection and evaluation during the welding process are of great significance for optimizing the production process, improving production efficiency and welding quality. However, in the process of resistance spot welding, the nucleation process of the nugget c...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/14
Inventor 罗怡
Owner CHONGQING UNIV OF TECH
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